Direction controlling means for selfstarting synchronous motors



Nov. 15, 1960 R. L. BERG 2,960,201

DIRECTION CONTROLLING MEANS FOR SELF-STARTING SYNCHRONOUS MOTORS Filed April 15, 1959 m'lrrlillllll I 50 34 4e g2 I l I llllll INVENTOR. RALPH L. Brae @BL/J/W ATTORNEY United States Patent DIRECTION CONTROLLING MEANS FOR SELF- STARTING SYNCHRONOUS MOTORS Ralph L. Berg, Crystal Lake, Ill., assignor to Controls Company of America, Schiller Park, 111., a corporation of Delaware Filed Apr. 13, 1959, Ser. No. 806,029

6 Claims. (Cl. 192-4) This invention relates to direction controlling means for use on self-starting electric synchronous motors of the type which, if not prevented from doing so, may start in either direction.

This invention is an improvement on Berg Patent No. 2,766,863, dated October 16, 1956. The direction controlling means employed in that device proved satisfac tory in operation but was objectionable because the helical spring created a clicking noise between the abutments on the first gear and the spring. The spring also proved costly in view of the relatively complicated nature of its formation and the additional operation required for its installation.

The principal object of this invention is to provide a noiseless, low cost direction controller.

The object has been realized by positioning a resilient plate on one gear of a gear train at a point in the train where it will engage and rebound from an adjacent gear if the train is started in the wrong direction. The plate is so designed that it will impart a small amount of load to the gear train and eliminate gear train noise inherent in an unloaded train,

As will be apparent hereinafter, this device is faster in operation due to the small amount of travel required before stopping rotation in the wrong direction. A further advantage of this device is that the gear train is continuously loaded so that noise inherent in an unloaded gear train is eliminated.

A still further advantage is that the device is simply and readily mounted on the gear train and afiords a considerable cost reduction.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings in which:

Figure 1 is a top plan view of a synchronous motor gear train embodying the present invention.

Figure 2 is a side elevation partly in section of a synchronous motor showing the present invention.

Figure 3 is a perspective view of the control element.

Referring to the drawings, numeral indicates generally a conventional, self-starting synchronous motor comprising stator 12 and a rotor shaft 14 carrying permanent magnet rotor 16 on which is fixed driv pinion 18. The stator and rotor are contained within housing 20 which includes a partition 22 provided with a central aperture 24 through which the drive pinion projects. This type of motor is reliably self-starting and, when energized, the rotor immediately rotates in synchronism, but may start in either direction of rotation. Accordingly, the rotation direction controlling means of my invention is provided so that the rotor 16 may operate only in one direction to drive any suitable mechanism. When blocked from rotation in one direction, the rotor will immediately start in the opposite or running direction.

The driving pinion 18 is operatively connected to a ICC conventional speed reducing gear train indicated generally by 26 and operatively connected to driven shaft 27. The first gear 28 of the train is mounted on the plate 22 and drives through pinion 30 to second gear 34 mounted on a shaft 35 which is provided with the rotation control or rebounding plate 36.

The rebound plate is positioned on the shaft 35 intermediate the second gear 34 and drive gear 40, and is formed of a thin sheet of resilient metal as shown in Figure 3. Plate 36 is mounted on shaft 35 so that it may slide on gear 34 and thus not interfere with the normal rotation of the gear train, and is held in position by gear 40. As will be seen, plate 36 includes a thin flat base portion 42 provided with an aperture 44 which is adapted to receive shaft 35. A pair of dimples 46 are provided in the body portion at a distance from the aperture 44 and rid on the upper surface of the second gear 34 to bow plate 36 between gears 34 and 40 and provide a slight frictional engagement between the plate and gear 34. The dimples serve a dual purpose; one, insuring that the plate will rotate with th gear in the wrong direction and providing a small amount of continuous load in the running direction. The dimples are not absolutely required for operation since it has been found that the plate will respond to the movements of the gear train in their absence.

At one end of the plate there is a projection 48 which is a continuation of the plate 36. This projection abuts the housing 20 in the running direction and limits the travel of the plate. The plate will not rebound upon impact with the housing because of the rigid nature of the projection. A Vertical finger is provided adjacent the projection 48 and has a tip 51 that engages pinion 30 as shown by dotted line in Figure l, to prevent rotation in the wrong direction. Upon engagement the finger is flexed slightly to impart a rebound to the gear so that the motor will reverse and start turning in the running direction,

In operation the stator 20 is energized and the rotor 16 begins to turn. If it starts in the wrong direction, the first gear 30 will turn less than one-half revolution whereupon tip 51 will engage the teeth of gear 30. In view of my prior patent, abutments could be provided on the pinion though this is considered a more costly approach. The finger 50 may be slightly flexed upon impact and the gear is prevented from rotation and correspondingly blocks rotation of the rotor 16. This finger 50 provides a slight yielding that imparts a small amount of rebound to the gear 30 in a reverse direction sufiicient to initiate smooth running of the motor in the required direction. When rotated in the running direction, th projection 48 hits the housing 20 and holds the plate 36 from further rotation. There will be no rebound of the plate when the projection hits the housing since the projection is a rigid structure and will not yield or flex to initiate any force in the opposite direction. A load is thereby continuously imparted to the gear train through member 36 and dimples 46 thus reducing inherent noise which is prevalent in an unloaded gear train.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In combination a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a first gear operatively engaging said pinion and driving a second gear, the second gear being mounted on a shaft and including a pinion gear, a thin resilient plate comprising a body portion having a central aperture, 2. projection and a vertical finger at one end, and a pair of dimples spaced from said aperture, said body portion being mounted on the common shaft intermediate the second gear and the pinion gear so that the finger will engage the first gear when rotated in one direction to block further rotation of the first gear and the projection will contact the housing when rotated in the opposite direction to prevent further rotationof th plate, said dimples slidably engaging the upper surface of the second gear to insure friction between the resilient plate and the second gear.

2. In combination a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a gear train operatively engaging said pinion, a thin resilient plate comprising a body portion having a central aperture therein and a projection and a vertical finger at one end, said body portion being mounted on a shaft of the gear train so that the finger will engage another gear in the gear train to prevent rotation of the gear train when the plat is rotated in one direction, and the projection will contact the housing when rotated in the opposite direction to prevent rotation of the plate with respect to the shaft when rotated in the opposite direction.

3. The combinaion with a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a gear train operatively engaging said pinion of a direction controlling means comprising, a member having a central aperture and a verticalfinger, said member being mounted on a shaft common to a driven gear and a pinion gear so that the vertical finger will engage an adjacent gear when the member is rotated in one direction, and the finger will engage the housing when rotated in the opposite direction preventing less than a half turn in the wrong direction of revolution.

4. A combination as set forth in claim 3 wherein said member includes a pair of dimples spaced from said aperture to slidably engage the driven gear.

5. The combination with a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a gear train operatively engaging said pinion, of a direction controlling means comprising, a plate mounted on a shaft of the gear train, means on the plate for engaging an adjacent gear when rotated less than a half turn in the wrong direction, means on the plate for insuring rotation of the plate in the wrong direction, means for preventing rotation of the plate in the running direction.

6. In combinatoin with a self-starting synchronous motor having a housing and a pinion on the rotor thereof, a gear train operatively engaging said pinion, a direction controlling means comprising, a plate mounted on a shaft of the gear train, means on the plate for engaging an adjacent gear in the gear train in less than a half turn of rotation in the wrong direction, said engaging means including means for imparting a rebound in the opposite direction to the adjacent gear, means for rotating said plate into the adjacent gear, and said engaging means also including means for preventing rotation of the plate in the running direction References Cited in the file of this patent UNITED STATES PATENTS 2,722,297 Gates Nov. 1, 1955 FOREIGN PATENTS 630,171 Great Britain Oct. 6, 1949 

